Many states offer a variation on a VoluntaryDisclosure Program, which allows taxpayers to abate penalties if they come forward to offer new information about existing tax liabilities.
Yes, many Americans have cheated by hiding income and assets in tax havens offshore, but they are now getting busted by the IRS. The U.S. Foreign Account Tax Compliance Act (FATCA) will force foreign banks to divulge information regarding their U.S. clients, and many offshore tax cheats are considering the extended IRS voluntarydisclosure program (see details below).